A power converter's efficiency (AC-DC or DC-DC) is determined by comparing its input power to its output power. For example, the efficiency of a power converter that provides 500 W of output power (Pout) and requires 625 W for the input power (Pin), is 80% (500 W/625 W=0.80). In this case, the input power exceeds the output power by 125 W or 20%, which is “wasted” power that is converted to heat energy which must be removed from the power converter by some cooling mechanism, such as thermal conduction, convection, and/or radiation.